To propose a heat exchanger of a dry dehumidifier having a heat exchange passage superior in a heat exchange rate, and hardly clogged with dust and dirt.

This heat exchanger 7 of the dry dehumidifier 1 is constituted by respectively joining both ends 73a and 73b of a plurality of resin pipes 73 to through holes 71a and 72a of an upper side installing plate 71 and a lower side installing plate 72 by thermal welding, and dews moisture included in indoor air by cooling the indoor air by exchanging heat with the indoor air A by passing high temperature-high humidity air through the inside of the respective resin pipes 73 after drying a hygroscopic filter of the dry humidifier by passing the indoor air A between the respective resin pipes 73. Since the heat exchange passage is formed without using an adhesive, air leakage is not caused in the heat exchange passage by hardening-separation of the adhesive, so that reduction in heat exchange efficiency is restrained. The heat exchange passage is formed of the resin pipes 73 to prevent a defect such as gathering of dust and dirt, and the occurrence of clogging caused by deformation of the heat exchange passage.